Combination visible light detector and ultraviolet detector coacting as a fire discrimination system

ABSTRACT

A combination visible light and ultraviolet flame detector is provided wherein a broad band solar cell senses the presence of a visible light source in a surveyed area, and a coacting ultraviolet detector confirms or negates the presence of any ultraviolet component in the visible light, thereby indicating whether the response signifies occurrence of fire, explosion, or merely a false alarm.

FIPBlOb AU Z33 United States Patent Cormier [4 1 Mar. 28, 1972COMBINATION VISIBLE LIGHT DETECTOR AND ULTRAVIOLET DETECTOR COACTING ASA FIRE DISCRIMINATION SYSTEM Arthur R. Cormler, Uxbridge, Mass.

The United States of America as represented by the Secretary of the AirForce Sept. 9, 1970 inventor:

Assignee:

Filed:

Appl. No.:

References Cited UNITED STATES PATENTS 3,544,792 12/1970 Giltaire..340/228 S X 3,122,638 2/1964 Steele et al..... 340/228 UX 3,246,3094/1966 Gasch, Jr. ..32l/49 X Primary Examiner-John W. Caldwell AssistantExaminer-William M. Wannisky Attorney-Harry A. Herbert, Jr. and GeorgeFine [57] ABSTRACT A combination visible light and ultraviolet flamedetector is provided wherein a broad band solar cell senses the presenceof a visible light source in a surveyed area, and a coacting ultravioletdetector confirms or negates the presence of any ultraviolet componentin the visible light, thereby indicating whether the response signifiesoccurrence of tire, explosion, or merely a false alarm.

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C'ftj' 7 /V 175726222 V /myrJ/Ma' 6 70 a2 r L 74 were .907 y La 2 C fa4C (ht 1 \5 BACKGROUND OF THE INVENTION The present invention relates toa flame detector, and more particularly to a flame detectordiscriminating flame from visible light.

Electrical systems for indicating when a condition under observation hasachieved a predetermined state utilize a transducer to translate thepresence of the condition into an electrical signal. In some instances,when the existence of flame or explosion is to be detected there is alsopresent visible light. It is particularly difficult, in the presence ofvisible light, to achieve an effective detecting system for flame orexplosion since the visible light would be translated into an electricalsignal in spite of the lack of flame or explosion. In the prior artthere does not exist a simple, effective detection system todiscriminate in the presence of both visible light and flame, orexplosion.

It is well known that flame or. explosion will result in the type ofradiation that will result in ultraviolet emission. This is particularlytrue in flame or explosion involving high temperatures.

The present invention, in sharp contrast to the prior art, utilizes apair of transducers, one exclusively for visible light and the other forultraviolet. The pair of transducers are arranged to survey theidentical area and coact so as to provide a unique detection systempermitting a discrimination to occur between visible light andultraviolet thereby providing a simple effective detector system.

SUMMARY OF THE INVENTION A combination visible light and ultravioletdetector system is provided. A broad band detector is employed to sensethe presence of a visible light source in the area under surveillance,and an ultraviolet detector confirms or denies the validity of theexistence of ultraviolet in the source of light. Should only visiblelight enter the region under surveillance, the ultraviolet detectorsensitive to light solely in the 2,300 A. region assumes a no-firecondition.

An object of the invention is to provide a two detector high temperatureultraviolet fire discrimination system.

Another object of the invention is to provide a visible light detectorin combination with an ultraviolet detector both surveying the identicalarea, one sensing the presence of visible light and the other confirmingor denying the presence of an ultraviolet component in the surveyingvisible light.

Still another object of the invention is to provide a fire detectionsystem combining an ultraviolet detector and a broad band solar celldetector to minimize false alarms and to provide high temperaturecapability.

These and other advantages, features and objects of the invention willbecome more apparent from the following description taken in connectionwith the illustrative embodiment in the accompanying drawing.

DESCRIPTION OF THE DRAWING A preferred embodiment of the invention isshown in block diagram form.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring in detailto the single FIGURE of the invention, there is shown broad band solarcell detector 1 and ultraviolet detector 6 both arranged and positionedto keep under surveillance the identical area. Broad band solar celldetector l is employed to sense in the area under surveillance thepresence of visible light source 10. Visible light source 10 may resultfrom fire, or explosion, et cetera. Detector l is av transducer with thecapability of transforming visible light into the representativeelectrical signal which is then assed throug amplifier 2 and received atthe input of gate 3. ate 3 is arranged to provide a gating output pulseupon the reception of an actuating signal from amplifier 2.

DC to AC converter 4 and high voltage power supply 5 develop the highvoltage for ultraviolet detector 6 and is energized only when "gated on"by an output signal from broad band solar cell detector 1. DC to ACconverter 4 receives a DC voltage from terminal 9. This gating techniqueprovides the advantage of time sharing the "on power of the converter tothe periods when broad band light impinges on detector 1. This techniquereduces the average power dissipation of all the components in thesystem and hence provides greater reliability and larger component life.

In addition, the limited "on time" of the electronics provides areduction of cooling requirements should the system be subjected toelevated temperatures. The cooling, in this case, may be passive andlimited to a covering of material possessing a low coefficient ofthermal conductivity.

When the converter is energized upon being gated on", high voltagesupply 5 delivers an actuating voltage to ultaviolet detector 6.Thereupon detector 6, in the presence of ultraviolet light source 11,will provide a representative electrical output signal which is passedthrough amplifier 7 to actuate alarm circuit 8 thus indicating thepresence of an ultraviolet signal. Alarm circuit 8 is conventional andmay be in the form of a visible, audible, or computer signal. It isemphasized again that broad band solar cell detector 1 and ultravioletdetector 6 are arranged to survey the identical area. In thisarrangement, detector 1 senses the presence of a source of visible lightand detector 6 confirms or denies the validity of existence of anultraviolet component in the source of visible light. Should onlyvisible light enter the area under surveillance, the ultravioletdetector, sensitive in this instance to light solely in the 2,300 A.region, would assume a no-fire condition. Thus the present inventionincludes a broad band solar cell detector which senses the presence of avisible light source in a surveyed area, and a coacting ultravioletdetector confirms or negates the presence of any ultraviolet componentin the visible light, thereby indicating whether the response signifiesoccurrence of fire, or explosion, or merely a false alarm.

What is claimed is;

l. A combination visible light detector and ultraviolet detectorcoacting as a fire and explosion discrimination system for a preselectedarea under surveillance comprising a broad band solar cell detectorpermanently operative, an ultraviolet detector normally inoperative andbecoming operative upon the receipt of a preselected high AC voltage,said broad band solar cell detector and said ultraviolet detector beingphysically and electrically positioned to simultaneously survey saidpreselected area, said broad band solar cell detector upon sensingvisible light characteristic of flame and explosion emanating from saidpreselected area providing a first electrical signal, means to generatea gating signal upon receipt of said first electrical signal, a DC to ACconverter arranged to be energized upon receipt of said gating signal toprovide an AC output voltage therefrom, said DC to AC converter alsoreceiving a DC input voltage, means to generate said preselected high ACvoltage for said ultraviolet detector upon said receipt of said ACoutput voltage, said ultraviolet detector upon becoming operativedetecting the presence of any ultraviolet component in the sensedvisible light characteristic of flame and explosion to provide a secondelectrical signal, and an alarm circuit becoming operative upon thereceipt of said second electrical signal.

1. A combination visible light detector and ultraviolet detectorcoacting as a fire and explosion discrimination system for a preselectedarea under surveillance comprising a broad band solar cell detectorpermanently operative, an ultraviolet detector normally inoperative andbecoming operative upon the receipt of a preselected high AC voltage,said broad band solar cell detector and said ultraviolet detector beingphysically and electrically positioned to simultaneously survey saidpreselected area, said broad band solar cell detector upon sensingvisible light characteristic of flame and explosion emanating from saidpreselected area providing a first electrical signal, means to generatea gating signal upon receipt of said first electrical signal, a DC to ACconverter arranged to be energized upon receipt of said gating signal toprovide an AC output voltage thErefrom, said DC to AC converter alsoreceiving a DC input voltage, means to generate said preselected high ACvoltage for said ultraviolet detector upon said receipt of said ACoutput voltage, said ultraviolet detector upon becoming operativedetecting the presence of any ultraviolet component in the sensedvisible light characteristic of flame and explosion to provide a secondelectrical signal, and an alarm circuit becoming operative upon thereceipt of said second electrical signal.